Question: atomic write algorithm

[mcollina]

As part of ipfs/js-ipfs#1785, I'm investigating what is the algorithm being used by the Go IPFS implementation to write chunks to disk. Can you point me to some code, or flesh it out in pseudocode?

[magik6k]

Assuming this is related to flatfs, the code lives in https://github.com/ipfs/go-ds-flatfs/blob/master/flatfs.go#L361

[Stebalien]

TL;DR:

1. Create a temporary file. (open)
2. Write to the temporary file. (write)
3. Close the temporary file. (close)
4. Atomically rename. (rename)
5. Sync the file. (sync)
6. Sync the directory. (sync)

The difference between go and js is that we don't use realpath (we don't really care about the real path).

[mcollina]

What go/fs/unix operation does sync file and sync directory operate?

[Stebalien]

"syncfs".

[mcollina]

Thanks!